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API · /number-api

Number API

healthy 4,754 Subscribers

A fast, fully-local number toolkit: spell numbers out in English words (great for amount-in-words on invoices and cheques), format ordinals (1st, 2nd, 112th), convert integers to and from Roman numerals (1 to 3999), convert numbers between any bases from 2 to 36, and format numbers locale-aware as decimal, currency or percent. Every endpoint accepts input via the query string or the request body. Pure server-side compute, no third-party upstream, so responses are instant and always available. Ideal for invoicing and billing, localization, education and developer formatting tooling.

#number #words #ordinal #roman #base-conversion #format #dev-tools
api.oanor.com/number-api
Get an API key Try in playground → Contact provider

Machine-readable spec so AI agents can integrate this API.

/api/number-api/openapi.json
/api/number-api/llms.txt

Discovery: GET /api/index.json lists every API.

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
143 ms
Server probes · 24h
Subscribers
4,754
active
Total calls
25
last 7 days
status Full status page → · 25 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 17,000 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 17,000 calls/month, 2 req/s
  • All endpoints: words, ordinal, roman, base, format
  • No credit card
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Basic

€4.00 /month

  • 270,000 calls / month
  • 12 requests / second
  • Hard cap (429 above quota, no overage)
  • 270,000 calls/month, 12 req/s
  • All endpoints incl. Roman 1-3999 and base 2-36
  • Commercial use allowed
  • Email support
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Pro

€12.00 /month

  • 1,600,000 calls / month
  • 40 requests / second
  • Hard cap (429 above quota, no overage)
  • 1,600,000 calls/month, 40 req/s
  • Locale-aware decimal, currency and percent formatting
  • Priority email support
  • Commercial use allowed
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Mega

€32.00 /month

  • 8,500,000 calls / month
  • 150 requests / second
  • Hard cap (429 above quota, no overage)
  • 8,500,000 calls/month, 150 req/s
  • Full toolkit at scale, deterministic low-latency compute
  • Priority support
  • Commercial use allowed
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Built by

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PremiumApi

Related APIs

Other APIs with overlapping tags.

Words API

Find words by meaning, sound and spelling — similar-meaning words (thesaurus), rhymes, autocomplete suggestions and wildcard spelling matches. Backed by Datamuse. Ideal for writing assistants, autocomplete, crosswords, word games, poetry tools and NLP preprocessing.

api.oanor.com/words-api

Dictionary API

Look up English word definitions with phonetic transcriptions, pronunciation audio, parts of speech and example sentences, plus synonyms and antonyms. Ideal for writing tools, word games, language learning and education apps. Experimental support for 11 more languages.

api.oanor.com/dictionary-api

XML API

A fast, fully-local XML toolkit: convert XML to JSON and JSON to XML with configurable attribute handling, validate XML well-formedness with line and column error details, and pretty-print XML while preserving element order. Every endpoint accepts input via the query string or the request body, up to 2 MB. Pure server-side compute, no third-party upstream, so responses are instant and always available. Ideal for system integrations, SOAP and legacy interop, RSS and sitemap processing, config tooling and data pipelines.

api.oanor.com/xml-api

DateTime API

A fast, fully-local date and time toolkit (UTC): parse any date string or unix timestamp into ISO, unix and components with the ISO week number, day-of-year and leap-year flag; format dates with custom tokens (YYYY-MM-DD, weekday and month names, and more); add or subtract month-aware durations; compute the difference between two dates in every unit plus a human-readable summary; and convert between unix timestamps and ISO. Every endpoint accepts input via the query string or the request body. Pure server-side compute, no third-party upstream, so responses are instant and always available. Ideal for scheduling, billing periods, reminders, analytics and any date arithmetic. (For the current time in a specific timezone, see the oanor Time API.)

api.oanor.com/datetime-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Number API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Number API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Number API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Number API cost?
Number API has a free tier with 100 calls / month. Paid plans start at €4.00 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Number API GDPR-compliant?
All requests to Number API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/number-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/number-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/number-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/number-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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